As is known in the art, signal isolators can be used to transfer information without a physical or electrical connection. For example, optocouplers can include a LED that emits light through an optically transparent insulating film (or dielectric) and strikes a photo detector that generates a current flow corresponding to the emitted light. RF carriers can also be used to transmit information through a barrier. Some known isolators use capacitive coupling and some known isolators use inductive coupling.
FIG. 1 shows a conventional signal isolator 10 having a split paddle with first and second isolated paddle portions 12a, 12b. A first die 14 is disposed on the first paddle portion 12a and a second die 16 is disposed on the second paddle portion 12b. The first die 14 is coupled to a first supply voltage 18, shown as VCC1, and the second die 16 is coupled to a second supply voltage 20, shown as VCC2. The isolator 10 passes signals between first and second domains, shown as VCC1 and VCC2, that are galvanically isolated from each other. Required isolation levels can be 15 kV or more for certain applications.
The first die 14 supports a first insulating layer 22 of dielectric material (e.g. SiO2, SiOH, Al2O3) and the second die 16 supports a second insulating layer 24. A first section of the first insulating dielectric 22 supports a first magnetic coil 26 (e.g. Al, Cu metallization) and the second insulating dielectric 24 supports a second magnetic coil 28. A first sensor 30, such as magnetic field sensing element, is located in proximity to the first coil 26, and a second sensor 32 is located proximate the second coil 28. A first signal 34 in the first domain (VCC1) is transmitted from the first die 14 to the second die 16 at the second coil 28 for detection by the second sensing element 32. A second signal 36 in the second domain (VCC2) is transmitted from the second die 16 to the first die 14 at the first coil 26 for detection by the first sensing element 30. Each coil/sensor pair provides magnetic coupling and serves to communicate signals between the two domains while maintaining galvanic isolation. The first and second die 14, 16 can include circuitry to process the signal from a respective sensor and/or control the cross-coupled coils.